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      <td width="400px"><p class="toc level1"><a href="docinfo.html">Document Information</a></p>
<p class="toc level1 tocsp"><a href="gexaf.html">Preface</a></p>
<p class="toc level1 tocsp"><a href="gfirp.html">Part&nbsp;I&nbsp;Introduction</a></p>
<p class="toc level2"><a href="bnaaw.html">1.&nbsp;&nbsp;Overview</a></p>
<p class="toc level2"><a href="gfiud.html">2.&nbsp;&nbsp;Using the Tutorial Examples</a></p>
<p class="toc level1 tocsp"><a href="bnadp.html">Part&nbsp;II&nbsp;The Web Tier</a></p>
<p class="toc level2"><a href="bnadr.html">3.&nbsp;&nbsp;Getting Started with Web Applications</a></p>
<p class="toc level2"><a href="bnaph.html">4.&nbsp;&nbsp;JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="giepx.html">5.&nbsp;&nbsp;Introduction to Facelets</a></p>
<p class="toc level2"><a href="gjddd.html">6.&nbsp;&nbsp;Expression Language</a></p>
<p class="toc level2"><a href="bnaqz.html">7.&nbsp;&nbsp;Using JavaServer Faces Technology in Web Pages</a></p>
<p class="toc level2"><a href="gjcut.html">8.&nbsp;&nbsp;Using Converters, Listeners, and Validators</a></p>
<p class="toc level2"><a href="bnatx.html">9.&nbsp;&nbsp;Developing with JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="gkmaa.html">10.&nbsp;&nbsp;JavaServer Faces Technology Advanced Concepts</a></p>
<p class="toc level2"><a href="bnawo.html">11.&nbsp;&nbsp;Configuring JavaServer Faces Applications</a></p>
<p class="toc level2"><a href="gkiow.html">12.&nbsp;&nbsp;Using Ajax with JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="gkhxa.html">13.&nbsp;&nbsp;Advanced Composite Components</a></p>
<p class="toc level2"><a href="bnavg.html">14.&nbsp;&nbsp;Creating Custom UI Components</a></p>
<p class="toc level2"><a href="bnafd.html">15.&nbsp;&nbsp;Java Servlet Technology</a></p>
<p class="toc level3"><a href="bnafe.html">What Is a Servlet?</a></p>
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<p class="toc level3"><a href="">Servlet Lifecycle</a></p>
<p class="toc level4"><a href="#bnafj">Handling Servlet Lifecycle Events</a></p>
<p class="toc level5"><a href="#bnafk">Defining the Listener Class</a></p>
<p class="toc level4 tocsp"><a href="#bnafn">Handling Servlet Errors</a></p>
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<p class="toc level3 tocsp"><a href="bnafo.html">Sharing Information</a></p>
<p class="toc level4"><a href="bnafo.html#bnafp">Using Scope Objects</a></p>
<p class="toc level4"><a href="bnafo.html#bnafs">Controlling Concurrent Access to Shared Resources</a></p>
<p class="toc level3 tocsp"><a href="bnafu.html">Creating and Initializing a Servlet</a></p>
<p class="toc level3"><a href="bnafv.html">Writing Service Methods</a></p>
<p class="toc level4"><a href="bnafv.html#bnafw">Getting Information from Requests</a></p>
<p class="toc level4"><a href="bnafv.html#bnafz">Constructing Responses</a></p>
<p class="toc level3 tocsp"><a href="bnagb.html">Filtering Requests and Responses</a></p>
<p class="toc level4"><a href="bnagb.html#bnagc">Programming Filters</a></p>
<p class="toc level4"><a href="bnagb.html#bnagd">Programming Customized Requests and Responses</a></p>
<p class="toc level4"><a href="bnagb.html#bnagf">Specifying Filter Mappings</a></p>
<p class="toc level5"><a href="bnagb.html#gjslc">To Specify Filter Mappings Using NetBeans IDE</a></p>
<p class="toc level3 tocsp"><a href="bnagi.html">Invoking Other Web Resources</a></p>
<p class="toc level4"><a href="bnagi.html#bnagj">Including Other Resources in the Response</a></p>
<p class="toc level4"><a href="bnagi.html#bnagk">Transferring Control to Another Web Component</a></p>
<p class="toc level3 tocsp"><a href="bnagl.html">Accessing the Web Context</a></p>
<p class="toc level3"><a href="bnagm.html">Maintaining Client State</a></p>
<p class="toc level4"><a href="bnagm.html#bnagn">Accessing a Session</a></p>
<p class="toc level4"><a href="bnagm.html#bnago">Associating Objects with a Session</a></p>
<p class="toc level4"><a href="bnagm.html#bnagq">Session Management</a></p>
<p class="toc level5"><a href="bnagm.html#gentextid-12885">To Set the Timeout Period Using NetBeans IDE</a></p>
<p class="toc level4 tocsp"><a href="bnagm.html#bnagr">Session Tracking</a></p>
<p class="toc level3 tocsp"><a href="bnags.html">Finalizing a Servlet</a></p>
<p class="toc level4"><a href="bnags.html#bnagt">Tracking Service Requests</a></p>
<p class="toc level4"><a href="bnags.html#bnagu">Notifying Methods to Shut Down</a></p>
<p class="toc level4"><a href="bnags.html#bnagv">Creating Polite Long-Running Methods</a></p>
<p class="toc level3 tocsp"><a href="gkcpg.html">The <tt>mood</tt> Example Application</a></p>
<p class="toc level4"><a href="gkcpg.html#gentextid-12965">Components of the <tt>mood</tt> Example Application</a></p>
<p class="toc level4"><a href="gkcpg.html#gkcoj">Building, Packaging, Deploying, and Running the <tt>mood</tt> Example</a></p>
<p class="toc level5"><a href="gkcpg.html#gkcob">To Build, Package, Deploy, and Run the <tt>mood</tt> Example Using NetBeans IDE</a></p>
<p class="toc level5"><a href="gkcpg.html#gkcpj">To Build, Package, Deploy, and Run the <tt>mood</tt> Example Using Ant</a></p>
<p class="toc level3 tocsp"><a href="bnagw.html">Further Information about Java Servlet Technology</a></p>
<p class="toc level2 tocsp"><a href="bnaxu.html">16.&nbsp;&nbsp;Internationalizing and Localizing Web Applications</a></p>
<p class="toc level1 tocsp"><a href="bnayk.html">Part&nbsp;III&nbsp;Web Services</a></p>
<p class="toc level2"><a href="gijti.html">17.&nbsp;&nbsp;Introduction to Web Services</a></p>
<p class="toc level2"><a href="bnayl.html">18.&nbsp;&nbsp;Building Web Services with JAX-WS</a></p>
<p class="toc level2"><a href="giepu.html">19.&nbsp;&nbsp;Building RESTful Web Services with JAX-RS</a></p>
<p class="toc level2"><a href="gjjxe.html">20.&nbsp;&nbsp;Advanced JAX-RS Features</a></p>
<p class="toc level2"><a href="gkojl.html">21.&nbsp;&nbsp;Running the Advanced JAX-RS Example Application</a></p>
<p class="toc level1 tocsp"><a href="bnblr.html">Part&nbsp;IV&nbsp;Enterprise Beans</a></p>
<p class="toc level2"><a href="gijsz.html">22.&nbsp;&nbsp;Enterprise Beans</a></p>
<p class="toc level2"><a href="gijre.html">23.&nbsp;&nbsp;Getting Started with Enterprise Beans</a></p>
<p class="toc level2"><a href="gijrb.html">24.&nbsp;&nbsp;Running the Enterprise Bean Examples</a></p>
<p class="toc level2"><a href="bnbpk.html">25.&nbsp;&nbsp;A Message-Driven Bean Example</a></p>
<p class="toc level2"><a href="gkcqz.html">26.&nbsp;&nbsp;Using the Embedded Enterprise Bean Container</a></p>
<p class="toc level2"><a href="gkidz.html">27.&nbsp;&nbsp;Using Asynchronous Method Invocation in Session Beans</a></p>
<p class="toc level1 tocsp"><a href="gjbnr.html">Part&nbsp;V&nbsp;Contexts and Dependency Injection for the Java EE Platform</a></p>
<p class="toc level2"><a href="giwhb.html">28.&nbsp;&nbsp;Introduction to Contexts and Dependency Injection for the Java EE Platform</a></p>
<p class="toc level2"><a href="gjbls.html">29.&nbsp;&nbsp;Running the Basic Contexts and Dependency Injection Examples</a></p>
<p class="toc level2"><a href="gjehi.html">30.&nbsp;&nbsp;Contexts and Dependency Injection for the Java EE Platform: Advanced Topics</a></p>
<p class="toc level2"><a href="gkhre.html">31.&nbsp;&nbsp;Running the Advanced Contexts and Dependency Injection Examples</a></p>
<p class="toc level1 tocsp"><a href="bnbpy.html">Part&nbsp;VI&nbsp;Persistence</a></p>
<p class="toc level2"><a href="bnbpz.html">32.&nbsp;&nbsp;Introduction to the Java Persistence API</a></p>
<p class="toc level2"><a href="gijst.html">33.&nbsp;&nbsp;Running the Persistence Examples</a></p>
<p class="toc level2"><a href="bnbtg.html">34.&nbsp;&nbsp;The Java Persistence Query Language</a></p>
<p class="toc level2"><a href="gjitv.html">35.&nbsp;&nbsp;Using the Criteria API to Create Queries</a></p>
<p class="toc level2"><a href="gkjiq.html">36.&nbsp;&nbsp;Creating and Using String-Based Criteria Queries</a></p>
<p class="toc level2"><a href="gkjjf.html">37.&nbsp;&nbsp;Controlling Concurrent Access to Entity Data with Locking</a></p>
<p class="toc level2"><a href="gkjia.html">38.&nbsp;&nbsp;Improving the Performance of Java Persistence API Applications By Setting a Second-Level Cache</a></p>
<p class="toc level1 tocsp"><a href="gijrp.html">Part&nbsp;VII&nbsp;Security</a></p>
<p class="toc level2"><a href="bnbwj.html">39.&nbsp;&nbsp;Introduction to Security in the Java EE Platform</a></p>
<p class="toc level2"><a href="bncas.html">40.&nbsp;&nbsp;Getting Started Securing Web Applications</a></p>
<p class="toc level2"><a href="bnbyk.html">41.&nbsp;&nbsp;Getting Started Securing Enterprise Applications</a></p>
<p class="toc level1 tocsp"><a href="gijue.html">Part&nbsp;VIII&nbsp;Java EE Supporting Technologies</a></p>
<p class="toc level2"><a href="gijto.html">42.&nbsp;&nbsp;Introduction to Java EE Supporting Technologies</a></p>
<p class="toc level2"><a href="bncih.html">43.&nbsp;&nbsp;Transactions</a></p>
<p class="toc level2"><a href="bncjh.html">44.&nbsp;&nbsp;Resource Connections</a></p>
<p class="toc level2"><a href="bncdq.html">45.&nbsp;&nbsp;Java Message Service Concepts</a></p>
<p class="toc level2"><a href="bncgv.html">46.&nbsp;&nbsp;Java Message Service Examples</a></p>
<p class="toc level2"><a href="gkahp.html">47.&nbsp;&nbsp;Advanced Bean Validation Concepts and Examples</a></p>
<p class="toc level2"><a href="gkeed.html">48.&nbsp;&nbsp;Using Java EE Interceptors</a></p>
<p class="toc level1 tocsp"><a href="gkgjw.html">Part&nbsp;IX&nbsp;Case Studies</a></p>
<p class="toc level2"><a href="gkaee.html">49.&nbsp;&nbsp;Duke's Tutoring Case Study Example</a></p>
<p class="toc level1 tocsp"><a href="idx-1.html">Index</a></p>
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<a name="bnafi"></a><h2>Servlet Lifecycle</h2>
<a name="indexterm-1068"></a><p>The lifecycle of a servlet is controlled by the container in which
the servlet has been deployed. When a request is mapped to a servlet,
the container performs the following steps.</p>


<ol><li><p><a name="indexterm-1069"></a>If an instance of the servlet does not exist, the web container</p>


<ol style="list-style-type: lower-alpha"><li><p>Loads the servlet class.</p>

</li>
<li><p>Creates an instance of the servlet class.</p>

</li>
<li><p>Initializes the servlet instance by calling the <tt>init</tt> method. Initialization is covered in <a href="bnafu.html">Creating and Initializing a Servlet</a>.</p>

</li></ol>
</li>
<li><p>Invokes the <tt>service</tt> method, passing request and response objects. Service methods are discussed in <a href="bnafv.html">Writing Service Methods</a>.</p>

</li></ol>
<p>If it needs to remove the servlet, the container finalizes the servlet by
calling the servlet&rsquo;s <tt>destroy</tt> method. For more information, see <a href="bnags.html">Finalizing a Servlet</a>.</p>



<a name="bnafj"></a><h3>Handling Servlet Lifecycle Events</h3>
<p><a name="indexterm-1070"></a><a name="indexterm-1071"></a>You can monitor and react to events in a servlet&rsquo;s lifecycle by defining listener
objects whose methods get invoked when lifecycle events occur. To use these listener
objects, you must define and specify the listener class.</p>



<a name="bnafk"></a><h4>Defining the Listener Class</h4>
<p><a name="indexterm-1072"></a><a name="indexterm-1073"></a>You define a listener class as an implementation of a listener interface. <a href="#bnafl">Table&nbsp;15-1</a>
lists the events that can be monitored and the corresponding interface that must
be implemented. When a listener method is invoked, it is passed an event
that contains information appropriate to the event. For example, the methods in the
<tt>HttpSessionListener</tt> interface are passed an <tt>HttpSessionEvent</tt>, which contains an <tt>HttpSession</tt>.</p>

<a name="bnafl"></a><p class="caption">Table&nbsp;15-1 Servlet Lifecycle Events</p><table><col width="21%"><col width="21%"><col width="57%"><tr><th align="left" valign="top" scope="column"><p>Object</p>

</th>
<th align="left" valign="top" scope="column"><p>Event</p>

</th>
<th align="left" valign="top" scope="column"><p>Listener Interface and Event
Class</p>

</th>
</tr>
<tr><td align="left" valign="top" scope="row"><p>Web context</p>

</td>
<td align="left" valign="top" scope="row"><p>Initialization and destruction</p>

</td>
<td align="left" valign="top" scope="row"><p><tt>javax.servlet.ServletContextListener</tt> and <tt>ServletContextEvent</tt></p>

</td>
</tr>
<tr><td align="left" valign="top" scope="row"><p>Web context</p>

</td>
<td align="left" valign="top" scope="row"><p>Attribute added, removed, or replaced</p>

</td>
<td align="left" valign="top" scope="row"><p><tt>javax.servlet.ServletContextAttributeListener</tt> and
<tt>ServletContextAttributeEvent</tt></p>

</td>
</tr>
<tr><td align="left" valign="top" scope="row"><p>Session</p>

</td>
<td align="left" valign="top" scope="row"><p>Creation, invalidation, activation, passivation, and timeout</p>

</td>
<td align="left" valign="top" scope="row"><p><tt>javax.servlet.http.HttpSessionListener</tt>, <tt>javax.servlet.http.HttpSessionActivationListener</tt>, and <tt>HttpSessionEvent</tt></p>

</td>
</tr>
<tr><td align="left" valign="top" scope="row"><p>Session</p>

</td>
<td align="left" valign="top" scope="row"><p>Attribute added, removed, or
replaced</p>

</td>
<td align="left" valign="top" scope="row"><p><tt>javax.servlet.http.HttpSessionAttributeListener</tt> and <tt>HttpSessionBindingEvent</tt></p>

</td>
</tr>
<tr><td align="left" valign="top" scope="row"><p>Request</p>

</td>
<td align="left" valign="top" scope="row"><p>A servlet request has started being processed by web components</p>

</td>
<td align="left" valign="top" scope="row"><p><tt>javax.servlet.ServletRequestListener</tt>
and <tt>ServletRequestEvent</tt></p>

</td>
</tr>
<tr><td align="left" valign="top" scope="row"><p>Request</p>

</td>
<td align="left" valign="top" scope="row"><p>Attribute added, removed, or replaced</p>

</td>
<td align="left" valign="top" scope="row"><p><tt>javax.servlet.ServletRequestAttributeListener</tt> and <tt>ServletRequestAttributeEvent</tt></p>

</td>
</tr>
</table><p><a name="indexterm-1074"></a>Use the <tt>@WebListener</tt> annotation to define a listener to get events for various
operations on the particular web application context. Classes annotated with <tt>@WebListener</tt> must implement one
of the following interfaces:</p>

<pre>javax.servlet.ServletContextListener
javax.servlet.ServletContextAttributeListener
javax.servlet.ServletRequestListener
javax.servlet.ServletRequestAttributeListener
javax.servlet..http.HttpSessionListener
javax.servlet..http.HttpSessionAttributeListener</pre><p>For example, the following code snippet defines a listener that implements two of
these interfaces:</p>

<pre>import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

@WebListener()
public class SimpleServletListener implements ServletContextListener,
        ServletContextAttributeListener {
    ...</pre>

<a name="bnafn"></a><h3>Handling Servlet Errors</h3>
<p>Any number of exceptions can occur when a servlet executes. When an exception
occurs, the web container generates a default page containing the following message:</p>

<pre>A Servlet Exception Has Occurred</pre><p>But you can also specify that the container should return a specific error
page for a given exception.</p>


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